1. Field of the Invention
The present invention relates to a two-dimensional solid-state image capture device and a polarization-light data processing method therefor.
2. Description of the Related Art
Two-dimensional solid-state image capture devices that obtain images through photography of subjects by using photoelectric conversion elements including two-dimensional solid-state image capture elements are increasingly used. Examples include a digital still camera, a video camera, and a camcorder (which is an integration of a photographing unit (such as a video camera) and a recording unit, and which is an abbreviation of a camera and recorder). CCD (charge coupled device) image capture elements and CMOS (complementary metal oxide semiconductor) image capture elements, which are solid-state image capture elements mainly used today, have sensitivities in a wide range from a visible-light wavelength to a near-infrared-light wavelength and can render vivid color images. The photoelectric conversion elements, however, have no intrinsic sensitivity to polarization. That is, the situation of the currently available two-dimensional solid-state image capture devices is that polarization information provided by light is unutilized and eliminated.
Although the sunlight is unpolarized, light resulting from reflection and dispersion of the sunlight contains polarization components that depend on the surface state of a reflection surface. For example, the sky during the daytime, snowy scenery, or the like contains a large amount of polarization component polarized in a particular direction. In addition, during photography across an “interface”, for example, during photography in which glass of a show window or the like is interposed or during photography at the surface of water, the surface of a lake, or the like, separation of polarization components and non-polarization components makes it possible to improve the image contrast and also makes it possible to eliminate unwanted information. For example, a polarization element can be advantageously used, for example, when it is desired to make a blue sky in a landscape picture to appear more ultramarine or it is desired to eliminate reflection components in a show window.
In general, in order to separate polarization components and non-polarization components, a polarizing (PL) filter is provided at the frontside of a lens and photography is performed with the polarization components being emphasized or attenuated through rotation of the polarizing filter. In terms of usability, however, such a scheme has some problems, for example, as follows.
[1] The polarization filter can only obtain polarization components in one direction at the same time.
[2] Only one type (one direction) polarization information can be obtained with the entire screen.
[3] Emphasis and attenuation of polarization components generally have to be adjusted through rotation of the polarizing filter.
The number of solid-state image-capture element pixels for use in the above-described two-dimensional solid-state mage capture device typically exceeds 10 millions. Due to a lithography-based microfabrication technology with advancement and improvement of semiconductor manufacturing processes, microstructures on a sub-100-nanometer scale have become feasible. Based on such a technological background, development and study of a solid-state image capture element that is capable of simultaneously obtaining polarization information, in addition to the capability of general photography, are also underway.
For example, Japanese Unexamined Patent Application Publication No. 2007-086720 discloses a device that simultaneously obtains polarization directions in four directions and intensities regarding polarization components (the intensities may hereinafter be referred to as “polarization component intensities”) to thereby obtain a polarization direction and a polarization component intensity. Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2007-501391 discloses a method and an optical element which cause surface plasmon polaritons in a wire grid (a conductor lattice).
Wire-grid polarization members have been used in a band of electromagnetic waves (e.g., mainly, microwaves, millimeter waves, and sub-millimeter waves) having longer wavelengths than visible-light wavelengths and have long been available as elements for separating frequencies and obtaining polarization components. In order to perform polarization component separation by using wire-grid polarization members, it is generally necessary to provide a wire grid with an interval (pitch) that is substantially the same as or smaller than the wavelength of electromagnetic waves. Thus, until recent years, it had been difficult to realize polarization members that are suitable for use in a visible-light wavelength band with wavelengths of 400 to 700 nm. However, with advancement and improvement of semiconductor manufacturing processes, polarization members that have reached the sufficiently practicable level even in a visible-light wavelength band are currently available. Future application of such wire-grid (conductor-lattice) polarization members is expected.